1. Field of the Invention
This invention relates to a position detection sensor, and a position detection device and a position input device incorporated with the position detection element.
2. Description of Related Art
Various conventional elements, devices, and methods used for detecting optically the position and motion of an object have been proposed and commercialized heretofore. In one example of a light detection element, a light detection layer and a resistance layer having an even resistance value are laminated to form a prescribed length of a laminate and an output electrode is provided on both ends thereof. In the light detection element, for example, a laser beam namely a light source is irradiated onto a light detection element, the photoelectric current generated thereby is measured at both ends to determine the laser irradiated position on the light detection element based on two current values. The above-mentioned light detection element may be formed in planer shape to detect the two-dimensional position or motion of an object.
However, in the above-mentioned method, it is required that an object must have a light source, and the light must be focused accurately on a light detection element. Therefore it is impossible for a light detection element to extract a moving object out of unspecified objects and to measure the position.
In another example of a method for detecting the position and motion of an object, an image pick-up element such as an area sensor of CCD (Charge Coupled Device) and an image memory are utilized. In this method, image information from an image pick-up element is stored in an image memory every prescribed time interval, and changed points of the image are extracted from a plurality of stored image information to detect the position and motion.
According to the method which utilizes CCD area sensor, moving objects are extracted from non-specific objects, and the position and motion are detected. However, a detection device which utilizes this method is inevitably large, and a memory having a large capacity and a high-speed operation CPU are required because of large image information to be processed, and such requirements makes disadvantageously the detection system very expensive.
It has been difficult to construct a position input device, for example, a pointing device such as a mouse because of the problem of the above-mentioned device.